When he was elected Labour leader on 12 September 2015 opinion was uniquely divided as to what impact Jeremy Corbyn would have on his party. Critics looked to his far-left politics and predicted disaster, believing Corbyn would repel millions of former Labour voters who had just re-elected a Conservative government committed to austerity; supporters believed his principled socialism would in contrast save the party by mobilising those alienated by Labour’s reluctant embrace of austerity.